Tag Archive for: flood plain

Photo Essay on Role of Riparian Vegetation in Reducing Erosion

Riparian means “of or relating to the banks of a river.” To see the role of riparian vegetation in reducing erosion, one need only compare the two forks of the San Jacinto River. They provide a stark contrast. But the real story is the role of sand mining in reducing riparian vegetation.

After years of sand mining on the West Fork, much of the shoreline vegetation has been lost and the resulting erosion is staggering. Between I-45 and US59, sand miners have stripped vegetation from approximately 20 square miles of floodplain and floodway (the main channel of a river during a flood).

Sand Mines on West Fork of the San Jacinto form an almost continuous line from I-45 to US59. They have stripped approximately 20 square miles of ground cover.

On the East Fork above the Caney Creek confluence, however, there are no sand mines. The vegetation is lush and the erosion is negligible. Let’s start there for a look at how nature protects us.

Forests come down to the river’s edge. Grasses and cattails abound, protecting the banks.

Dense forest anchors the land. Grasses, forced to compete for sunlight, thrive along the river’s edge, protecting banks.

A perfect time and place for reflection. A nice place just to “be.”

All images so far were taken on the East Fork of the San Jacinto River above where it merges with Caney Creek. Image courtesy of Google Earth.

Red lines on left measure width of East Fork on 3/3/16, before the Tax Day Storm. They are in a separate layer. Switching the background image to 10/28/17 shows that the river is virtually unchanged, thanks in large part to the lush riparian vegetation.

Now, A Trip up the West Fork

Now, let’s look at the West Fork. It’s vastly different.

Townhomes on Marina Drive in Forest Cove. Concrete, steel and wooden walls on the West Fork were less effective at preventing erosion than blades of grass on the East Fork.

Same area. Note steepness of banks where vegetation can no longer take hold, perpetuating cycles of erosion.

Remnants of concrete retaining wall.

Site of a breach in sand mine dike on the West Fork. The mine discharged sediment directly into the river.

Two weeks after Harvey. Just north of US 59 bridge.

West Fork Sand mine complex. Note one of many dike breaches in various mines that allowed sand and sediment to pour downstream. All helicopter images taken two weeks after Harvey on 9/14/17.

Mining a point bar after Harvey. Miners are supposed to work within their dikes to avoid disrupting vegetation along the river. Photo taken 9/14/17.

Note more repairs to dikes.

The next three images form a series.

River is migrating toward pit in background at the rate of 12 feet per year, in part, due to lack of vegetation protecting banks. See next two images before for overhead views.

This is what the area above looked like in a 1995 USGS aerial photo on Google Earth. Compare the location of the red line in this image with the location in the next image. The GPS coordinates of the line are identical. But the river has migrated.

 In just 23 years, the West Fork migrated 258 feet toward the dike on the right and now threatens it. The river has eaten away at the dike an average of 12.4 feet per year. The dike is now only 38 feet wide.

A bright white trail of sand leads all the way from the mines to the mouth bar which helped back water up into the highly populated Humble/Kingwood area. Fresh sand is several feet deep. Note absence of grasses. Many of the trees will also soon die.

Nearing the US59 bridge

Confluence of West Fork and Spring Creek, which also contributed sand to this event.

The next two images form a before/after pair.

West Fork of the San Jacinto over the US 59 Bridge before the Tax Day flood in 2016. River was 330 feet wide. Image courtesy of Google Earth.

GPS coordinates of the red line have not changed; the river has. After Harvey (in a little more than two years), the West Fork widened to 489 feet and shifted north by 113 feet. In part, this was due to excessive sediment that killed vegetation along the banks and accelerated erosion. Dead trees swept downriver were trapped by the bridge pilings, forming a dam that helped flood Humble businesses south of this photo. The southbound lanes of the bridge had to be replaced by TexDoT at a cost of approximately $20 million because of erosion. 

Union Pacific railroad traffic was disrupted for months.

Mountains of sand may kill the remaining trees in this area, exposing it to even more erosion during the next storm.

Sand, in part, from the mines, has almost totally blocked the West Fork where it meets Lake Houston. Before/after measurements show that as much as ten feet was deposited in this area during Harvey (approximately five feet below water and five above). This forms a dam behind the dam, that backs water up into the Humble/Kingwood corridor during storms. Unless this sediment is removed, a storm smaller than Harvey could create Harvey-scale flooding.

Tree Loss in East End Park Has Already Started

Acres of trees in Kingwood’s East End Park have already started to die back as a result of being buried in dunes 10-15 high. I believe that sand, in large part, from the 750-acre mine upstream on Caney Creek is causing this. Piling as little as six inches of sediment around the base of a tree can kill it.

Trees dying in Kingwood’s East End Park because of massive sediment build up around their trunks.

The website SF Gate describes how this die-back happens. “Soil added around a tree reduces the amount of oxygen available to the roots and slows the rate of gas exchange in and around the roots. There may be less moisture and nutrients available to the roots or too much moisture may remain around the tree’s roots. Inadequate oxygen reaching the roots or microorganisms in the soil around the roots can lead to an accumulation of chemicals that can injure tree roots. The tree’s bark may decay where soil is newly in contact with it. Damage or injury to the tree because of the added soil may not become apparent for several months or years and generally appears as a slow decline followed by death.” The same thing can happen with grasses and smaller trees along riverbanks. Once they die back and there is nothing left to bind the soil…

“Sediment is the primary pollutant expected from quarry operations.”

The Texas Commission on Environmental Quality says, “Sediment is the primary pollutant expected from quarry operations.” See page 22 of this 2012 report from the Texas Commission on environmental quality about the John Graves Scenic Riverway District on the Brazos.  The TCEQ also conducted experiments showing that certain types of revegetation can reduce sediment discharge from mines by 98 percent.

These findings are consistent with Louisiana Best Management Practice Guidelines for Sand Mines. They state that grasses can reduce erosion by 99%.


In the upcoming legislative session, the Lake Houston area needs to push for the creation of a river preservation district like the John Graves. The Graves District excludes sand mines from the 100-year flood plain and floodway where most erosion happens.

All Lake-Houston-area mines are in the FLOODWAY with the exception of one. A floodway is defined as the main channel of the river during a flood. This makes the mines more susceptible to river capture and massive erosion, which can create a downward spiral as we have seen above. Eventually it can lead to loss of property.

Our preservation district would stretch from Lake Conroe to Lake Houston, the primary sources of water for two million people.

The lives, health, homes, and businesses of two million people are certainly worth as much as protecting some scenery.

Posted by Bob Rehak on 12/1/18

449 Days after Hurricane Harvey

Sand Mining Best Management Practices: Vegetation

Sand mining best practices throughout the country and the world urge operators to leave vegetation in place until they are ready to mine an area. The reason: to reduce erosion. However, approximately 60 acres of the sand mine below on the East Fork of the San Jacinto where it meets Caney Creek and White Oak Creek was cleared but not mined – just in time for two 500-year floods.

Approximately 65 acres of this mine were cleared before two five-hundred year floods, contributing to downstream sedimentation in the East Fork, even though only about three acres of the area was mined.

Removing Vegetation Risks Sedimentation Downstream

The cleared area lies totally in the 100-year flood plain and was inundated. Satellite images of the area downstream from the cleared land show a sudden buildup of sand. While the sand did not all come from the cleared area, one wonders how much sedimentation could have been prevented by following best practices.

The following sequence of images shows the rapid removal of vegetation.

The white outlined area will be totally cleared before Harvey. On April 8, 2014, it was all dense forest. 

By March 3, 2016, most of the area was cleared.

By January 23, 2017, just before Harvey, the area was entirely cleared.

Risk from Flooding

This FEMA flood hazard map shows that the entire area lies within with 100-year flood plain (aqua) and adjacent to the floodway (cross-hatched area).

Before and After: Results

This image from 2014 shows the area in question when it was still forested. Note how little sand is in the river downstream from the mine.

Here’s the same view after vegetationwas cleared and the area was inundated by Harvey in 2017. Note all the sediment in the river downstream.

Much of the sand and sediment washed downstream is invisible to satellite photos because it’s under dense forest canopy. This area (downstream the sand mine being discussed) was once wetlands. A boardwalk through those wetlands had to be excavated from several feet of sand after Harvey.

Here’s what part of the same trail looked like before it was excavated. Approximately 30 acres of the park were blanketed with dunes up to 10 feet tall after Harvey. Every trail in the park required repairs. Total cost: approximately $200,000 to Kingwood residents.

A bird’s nest that was ten feet up in a tree is now knee high. Many of the trees along the Eagle Point trail in East End Park are buried under so much sand that they are dying. 

An Ounce of Prevention

It’s impossible to tell how much of the sand above resulted from the removal of vegetation?  Previous posts showed how the mines stockpile also eroded. The river itself contributed sediment. However, if the mine were not in the flood plain and if the miners had not removed so much vegetation so far in advance of mining, we wouldn’t be having this discussion.

So why do miners favor the floodplains and floodways? Why to they remove vegetation years before it will be mined? Is it all about the relentless pursuit of efficiency at the expense of safety?

Tomorrow, we will look at economics, taxation and how some well-intentioned laws passed in the late seventies to protect family farms helped fuel a boom in sand mining.

Posted September 24, 2018

391 Days since Hurricane Harvey

Montgomery County Floodplain Management Regulations Affecting Sand Mines: Are They Being Enforced?

A friend called my attention to Montgomery County Floodplain Management Regulations.  These regulations govern permitting of sand mines in the county. The thoughts are great. But are the regulations being enforced? Are they actually protecting the people of Montgomery County and residents downstream? You be the judge.

Findings of Fact

The regulations start out with “Findings of Fact.” They state on page 4:

“The flood hazard areas of Montgomery County are subject to periodic inundation, which results in loss of life and property, health and safety hazards, disruption of commerce and governmental services, and extraordinary public expenditures for flood protection and relief, all of which adversely affect the public health, safety and general welfare.” Also…

“These flood losses are created by the cumulative effect of obstructions in flood plains which cause an increase in flood heights and velocities, and by the occupancy of flood hazard areas by uses vulnerable to floods and hazardous to other lands because they are inadequately elevated, flood-proofed or otherwise protected from flood damage.”

When they wrote that last statement, they may not have anticipated the specific problem of the giant sandbar at the mouth of the San Jacinto River, but it certainly applies. The bar is backing water up throughout Humble, Kingwood and Atascocita,  and it was created – in part – with sand that came from mines built in the West Fork floodway.

The second part of that last statement about “inadequately elevated, flood-proofed or otherwise protected from flood damage” also applies.  Common-sense best management practices required in other states could have helped protect us. Those include moving mines out of the floodway, not mining below the thalweg, greater setbacks from the river, wider dikes with more gradual slopes, replanting areas already mined, and more. If only those BMPs were practiced here!

Statement of Purpose

Also on page 4, the next section, “Statement of Purpose,” says, “It is the purpose of these regulations to promote the public health, safety and general welfare and to minimize public and private losses due to flood conditions in specific areas by provisions designed to: 

  1. Protect human life and health; 
  2. Minimize expenditure of public money for costly flood control projects; 
  3. Minimize the need for rescue and relief efforts associated with flooding and generally undertaken at the expense of the general public; 
  4. Minimize prolonged business interruptions; 
  5. Minimize damage to public facilities and utilities such as water and gas mains, electric, telephone and sewer lines, streets and bridges located in flood plains

Just downstream from River Grove Park in Kingwood, a new sandbar has formed on the west fork of the San Jacinto. Boats that draw 18 inches of water can no longer navigate upstream (foreground) past this sandbar.

Primary Threat of Sand Mining

The primary threat from sand mines is sand and sediment that washes out of the mines during floods and accelerates the natural rate of sedimentation. Sand mine pits probably lower floods within THEIR local area by a small amount. No argument there.

However, when the West Fork of the San Jacinto River captures the pits (as it has done repeatedly), large volumes of sediment can be swept downstream and contribute to flooding elsewhere. The professional engineer that certified the development plans of these sand mines should have anticipated this, especially downstream of the Lake Conroe Dam.

Google Earth shows many instances of river capture and not just in Harvey. Much smaller floods have captured pits, too. These repeated captures are caused by building mines in floodways, excavating too close to the river, and using dikes/levees that are insufficient to withstand the volume of floodwaters – especially when the San Jacinto River Authority releases water from the Lake Conroe Dam. Additionally, mines sometimes increase the height of their levees by piling up sand in a way that constricts the floodway.

As You Review these Regulations…

I reviewed these regulations as I thought about the thousands of homes and businesses flooded downstream from the mines, partially as a result of massive sand bars that that blocked drainage ditches and the river itself (see photo above).

Clearly, not all of that sand came from mines, but some did. I flashed on the City Sewage Facility that was inundated, the loss of six buildings at Kingwood College that were contaminated by that sewage, and the $70 million taxpayers will spend on a dredging project…that doesn’t even address the biggest sand blockage on the river.

The most obvious areas to explore for permit violations include:

Article IV

  • Sec (B)(2) Ensure that the proposed … site … will be reasonably safe from flooding (page 15)
  • Sec (C)(2)(c)  Consider the danger that materials may be swept onto other lands to the injury of others. (Page 17)
  • Sec (C)(2)(f) Consider the costs of providing governmental services during and after flood conditions including maintenance and repair of streets and bridges, and public utilities and facilities such as sewer, gas, electrical and water systems. (Page 17)
  • Sec (C)(2)(g) Consider the expected heights, velocity, duration, rate of rise and sediment transport of the floodwaters and the effects of wave action, if applicable, expected at the site. (Page 17)
  • Sec (C)(2)(c) Permits should be denied if there’s a danger that materials could be swept onto other lands to the injury of others. (Page 17)
  • Sec (D)(2)(b) Variances shall not result in increased flood heights, threats to public safety, extraordinary public expense, create a nuisance or victimize the public. (Page 18)
  • Sec (D)(10) Any person or persons aggrieved by the decision of the Commissioners Court may appeal such decision in a court of competent jurisdiction. (Page 19)

Article V

  • Sec (A)(2) All improvements shall be constructed by methods and practices that minimize flood damage. (Page 21)
  • Sec (A)(8) An engineer must certify that the proposed excavation will have no adverse impact to the drainage on, from or through adjacent properties. (Page 21)

Article VI

  • Sec (E)(1) Permits can be revoked in cases where there has been a false statement or misrepresentation. (Page 27)
  • Sec (E)(5) Violators can be fined $100 per day for each violation. (One of those dikes remained open for 3 years and another for 8!) (Page 28)
  • Sec (E)(7) A permit holder in violation may be forced to restore property to pre-existing conditions. (Page 28)
To read the complete regulations, click here. As stated on pg 26,  SECTION F. EXEMPTIONS (5)  Commercial mining and dredging are not exempt and must have a professional engineer certify the development plans of sand mines. Therefore, one would expect that the engineer would have evaluated sediment transport from the mines and the potentially increased risk of downstream flooding – especially downstream of the Lake Conroe Dam.
As always, these are my opinions on matters of public policy, protected by the First Amendment of the U.S. Constitution and the Anti-SLAPP statutes of the great State of Texas.
Posted August 6, 2018 by Bob Rehak
342 Days since Hurricane Harvey